Apparatus and method for specimen fabrication

ABSTRACT

A specimen fabricating apparatus comprises: a specimen stage, on which a specimen is placed; a charged particle beam optical system to irradiate a charged particle beam on the specimen; an etchant material supplying source to supply an etchant material, which contains fluorine and carbon in molecules thereof, does not contain oxygen in molecules thereof, and is solid or liquid in a standard state; and a vacuum chamber to house therein the specimen stage. A specimen fabricating method comprises the steps of: processing a hole in the vicinity of a requested region of a specimen by means of irradiation of a charged particle beam; exposing the requested region by means of irradiation of the charged particle beam; supplying an etchant material, which contains fluorine and carbon in molecules thereof, does not contain oxygen in molecules thereof, and is solid or liquid in a standard state, to the requested region as exposed; and irradiating the charged particle beam on the requested region as exposed.

CLAIM OF PRIORITY

The present invention claims priority from Japanese Application No.2005-154875 filed on May 27, 2005, the contents of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus and a method offabricating a specimen for observation of a structure, which is used toobserve a cross sectional shape of a device or the like.

There have been increased needs for examination and analysis ofsemiconductor devices, for which miniaturization is going to progress.In a failure analysis, which specifies the cause of failure, among theneeds, it is an essential technology to directly observe a defect insidea device. Method of observing a section is shown in. FIGS. 2A and 2B. Inthe beginning, focused ion beam (referred below to as FIB) 201 is usedto process a rectangular hole 202, of which one side defines a positionbeing requested for section observation. One side of the hole formedthereby defines a requested section 203, and the section is observed bya scanning electron microscope (referred below to as SEM). Since thesection is formed by irradiating FIB 201 in parallel to the requestedsection, the section formed by FIB is essentially flat. On the otherhand, SEM used for observation irradiates primary electrons in aposition of observation and imaging, as contrast, the number ofsecondary electrons (or reflected electrons) generated from the positionto thereby form an image to be observed. While the number of secondaryelectrons depends upon material of an object, it depends upon anirregular shape further than that. That is, since an observation section203 formed by FIB is flat as described above and little irregular inshape, a difference in SEM image contrast consists of only a differencein secondary-electron yield attributable to a material. However, only adifference, in secondary-electron yield, attributable to a material isinsufficient for that observation of a minute structure, the necessityof which has been increased in recent years, and so there is caused aproblem that the image resolution is insufficient.

Therefore, it is desirable to emphasize a contrast differenceattributable to a structure. As measures for realizing this, there isused decoration of profile by forming irregularities every material of astructure. In SEM, when irregularities are present, boundaries of raisedportions are observed to be bright since edges become large insecondary-electron yield, so that observation in high contrast is madepossible. In order to provide for a difference in level every structure,a difference in processing sputtering yield, attributable to a material,is made use of. In case of FIB, since a difference in sputtering yield,attributable to a material, is present also in physical sputtering,irregularities 301, 302, 303 every material can be formed as shown inFIGS. 3A and 3B by irradiating FIB not in parallel to a section butobliquely at a certain angle to a section. FIG. 3B shows a section whena section indicated by a broken line in FIG. 3A is viewed along an arrow304, and a left side thereof defines an outermost surface. For example,structures 301, 303 are made of Si and a structure 302 is made of SiO₂.Here, the reason why FIB is irradiated obliquely is that since a sectionis defined by a side of a processed hole, irradiation perpendicular tothe section is impossible. Since a difference in sputtering yield,attributable to a material, is relatively small, however, an intenseprocessing on a section is needed to form sufficient irregularities byphysical sputtering with FIB, which causes a problem in terms of damage.

Therefore, methods of efficiently forming irregularities depending upona material include a processing making use of chemical reaction. Forexample, Japanese Patent No. 3216881 indicates that irregularities dueto differences in sputtering rate can be formed by performing a FIBprocessing while making fluorine-containing gases flow to a processedsample. Japanese Patent No. 3350374 discloses FIB assist-etchantmeasures, in which halogenated gases and halogenated hydrocarbon gasessuch as Cl₂, XeF₂, CF₄, CHF₄, C₂F₆, C₃F₈, C₄F₈, etc. are used asetch-assisting gases. U.S. Pat. No. 6,211,527 discloses measures torealize decoration of a section by means of FIB assist-etchant, in whichhalogenated hydrocarbon gases are used as etch-assisting gases.

By performing FIB assist-etchant with the use of etch-assisting gases asin the related art, it is possible to vary a processing speed everymaterial. As described above, a difference in level of irregularities isimportant in order to provide for a difference in contrast in SEMobservation. However, an excessive processing with a view to forming adifference in contrast is not desirable. The reason for this is a fearthat in case of FIB, since the presence of irregularities brings aboutan increase in sputtering rate at edge portions, the edge portions getout of shape to look differently in SEM observation from an originalstructure of a section. Further, digging much by means of FIB in orderto provide for a difference in level means that a structural profiledifferent from a section being essentially observed is observed in adevice, which is varied in structure in a depthwise direction.Therefore, it is desirable to make an amount of processing as small aspossible to form a necessary difference in level.

Gases adopted in Japanese Patent Nos. 3216881 and 3350374 are in essencegaseous in a standard state. The standard state means 1 barometricpressure and 25° C. Essentially, these gases are those used in plasmaetchant. In case of plasma etchant, gases themselves are ionized asplasma and ionized molecules are accelerated by plasma sheath formed ona surface of a sample, being a target of processing, to be irradiated ona surface of the sample, thereby performing etchant. However, FIBassist-etchant is different in reaction configuration in the followingmanner. Etch-assisting gases as supplied are first adsorbed by a samplesurface. FIB is irradiated on the sample surface to inject energythereinto to give thereto a reaction energy for reaction of aconstituent material of a sample with gases, thereby generating achemical reaction to subject a material of the sample to etchant.Therefore, in order to adequately cause the reaction, it is requiredthat gases be sufficiently adsorbed by the sample surface. However, theprobability that the gases being originally gaseous at room temperatureare physically adsorbed by the sample surface is small as compared witha substance being originally solid, so that it is difficult to ensure asufficient adsorbed amount. That is, gases used in plasma etchant is notnecessarily suited to FIB etch-assisting gases.

Further, a material accounting for a large part of a semiconductordevice comprises silicon (Si) being a substrate material and an oxidesilicon (SiO₂, etc.) being an insulating material. While it is desirableto form a difference in level between Si and SiO₂, the reason why the CFgases are used is as follows. Si reacts chemically with F to generatevolatile SiF₄ or the like to be etched. In this case, however, C remainswhereby a substance, such as SiC, etc., being hard to be etched isformed to suppress etchant. On the other hand, with SiO₂, Si volatilizesas SiF₄ or the like as described above and C also reacts with O tovolatilize as CO₂ or the like, so that etchant is not suppressed likeSi. Thereby, Si and SiO₂ are varied in sputtering rate, so that itbecomes possible to create a difference in level. CF gases, such as CO,COOH, etc., which contain O, are adopted in the U.S. Pat. No. 6,211,527.While SiC serves to suppress Si etchant in the reaction, O contained inetchant gases involves a fear that such suppressing effect is decreased.Therefore, there are needed an apparatus and a method of fabricating asection, in which the problems are solved, an effective difference inetchant is ensured, and a requested difference in level is fabricated inless processing to enable realizing a high contrast observation withSEM.

SUMMARY OF THE INVENTION

In order to solve such problems, the invention provides a specimenfabricating apparatus and a specimen fabricating method described below.

A specimen fabricating apparatus according to the invention comprises amovable specimen stage, on which a specimen is placed, a chargedparticle beam optical system that irradiates a charged particle beam onthe specimen, an etchant material supplying source that supplies anetchant material, which contains fluorine and carbon in moleculesthereof, does not contain oxygen in molecules thereof, and is solid orliquid in a standard state (1 barometric pressure and 25° C.), and avacuum chamber that houses therein the specimen stage. Thereby, itbecomes possible to fabricate a specimen profile of which is decorated.

A specimen fabricating apparatus according to the invention comprises amovable specimen stage, on which a specimen is placed, a chargedparticle beam optical system that irradiates a charged particle beam onthe specimen, an etchant material supplying source that supplies anetchant material, in molecules of which a ratio of fluorine to carbon innumber is 2 or more and which is solid or liquid in a standard state (1barometric pressure and 25° C.), to the specimen, and a vacuum chamberthat houses therein the specimen stage. Thereby, since a furtherdifference in sputter rate can be ensured, it becomes possible toeffectively fabricate a specimen profile of which is decorated.

A specimen fabricating method according to the invention comprises thesteps of processing a hole in the vicinity of a requested region of aspecimen by means of irradiation of charged particle beam, exposing therequested region by means of irradiation of charged particle beam,supplying an etchant material, which contains fluorine and carbon inmolecules thereof, does not contain oxygen in molecules thereof, and issolid or liquid in a standard state (1 barometric pressure and 25° C.),to the requested region as exposed, and irradiating a charged particlebeam on the requested region as exposed. Thereby, it is possible torealize fabrication of a specimen profile of which is decorated.

A specimen fabricating method according to the invention comprises thesteps of processing a hole in the vicinity of a requested region of aspecimen by means of irradiation of charged particle beam, exposing therequested region by means of irradiation of charged particle beam,supplying an etchant material, in molecules of which a ratio of fluorineto carbon in number is 2 or more and which is solid or liquid in astandard state (1 barometric pressure and 25° C.), to the specimen, andirradiating a charged particle beam on the requested region as exposed.Thereby, since a further difference in sputter rate can be ensured, itbecomes possible to effectively fabricate a specimen profile of which isdecorated.

According to the invention, a device section can be simply observed bymeans of SEM with high accuracy, so that it is possible to realize afailure analysis in a short time and to achieve an improvement in yieldin semiconductor process.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an example of a construction of a specimenfabricating apparatus according to the invention;

FIGS. 2A and 2B are views illustrating a method of FIB assistingetchant;

FIGS. 3A and 3B are views showing a section after an assisting etchantsection processing;

FIG. 4 is a view showing a schematic construction of an etch-assistinggas source in the invention;

FIG. 5 is a view showing, in enlarged scale, the etch-assisting gassource;

FIG. 6 is a view showing a state, in which the etch-assisting gas sourceis mounted to the apparatus;

FIG. 7 is a view showing a construction of a cartridge typeetch-assisting gas source;

FIG. 8 is a view illustrating a way to mount the cartridge;

FIG. 9 is a view illustrating an example of a procedure of a specimenfabrication method according to the invention;

FIG. 10 is a view showing an example of a construction of a specimenfabricating apparatus, according to the invention, for decoration of asection of a micro-sample;

FIG. 11 is a view illustrating a procedure of a processing of amicro-sample according to the invention;

FIG. 12 is a view illustrating a procedure for decoration of a sectionof a micro-sample according to the invention;

FIG. 13 is a view showing an example of a construction of a FIB-SEMapparatus according to the invention;

FIG. 14 is a view illustrating a method for decoration of a section ofan extracted micro-sample according to the invention;

FIG. 15 is a view showing an example of a construction of a FIB-SEMapparatus, according to the invention, with a non-inclined specimenstage;

FIGS. 16A and 16B are views illustrating a procedure of a processing fordecoration of a section, according to the invention, with the use of thenon-inclined specimen stage;

FIG. 17 is a view showing an example of a construction of a PJIBapparatus according to the invention; and

FIG. 18 is a view showing an example of a construction of an electronbeam apparatus according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

An explanation will be given below to concrete embodiments of anapparatus for fabricating a specimen and a method of fabricating aspecimen, by which beam-assisting etchant with the use of effectiveetch-assisting gases can be used to fabricate minute irregularitiesevery structure on a section of a specimen for a section SEMobservation.

Embodiment 1

FIG. 1 shows a construction of a specimen fabricating apparatus forfabricating an observe section making use of focused ion beam. Thespecimen fabricating apparatus comprises a movable specimen stage 102,on which a specimen substrate such as a semiconductor wafer 101, etc. isplaced, a specimen position controller 103 that controls a position ofthe specimen stage 102 to observe the wafer 101 and specify a positionof processing, an ion-bean irradiating optical system 105 thatirradiates an ion beam 104 on the wafer 101 for processing, and asecondary-electron detector 106 that detects secondary electrons emittedfrom the wafer 101. The ion-bean irradiating optical system 105 iscontrolled by a controller 107 for the ion-beam irradiating opticalsystem, and the secondary-electron detector 106 is controlled by acontroller 108 for the secondary-electron detector. An etch-assistinggas supplying source 109, which supplies an etch-assisting gas forformation of irregularities on a section every material, that is,decoration of a section, is controlled by a controller 110 for theetch-assisting gas supplying source with respect to a position thereof,heater temperature, valve opening and closing, and the like. Thecontroller 107 for the ion-beam irradiating optical system, thecontroller 108 for the secondary-electron detector, the controller 110for the etch-assisting gas supplying source, the specimen positioncontroller 103, etc. are controlled by a central processing unit 111.The specimen stage 102, the ion-bean irradiating optical system 105, thesecondary-electron detector 106, the etch-assisting gas supplying source109, etc. are arranged in a vacuum chamber 112. Here, a specimen is awafer, and the fact that it is possible to observe in a state of a waferis advantageous in that it is easy to control addresses of positions, ofwhich observation is requested, and a wafer can be transferred as it isfrom an examining device. However, decoration of a section is possiblefor a chip specimen, and so a specimen chamber and a specimen stage maybe constructed so that they can be formed to be small and simple. Thiscase is advantageous in terms of device cost since manufacture isenabled at low cost.

FIG. 4 shows a schematic construction of an etch-assisting gas source.According to the embodiment, a material being solid or liquid in astandard state is used as an etch-assisting gas material 401, and sothere is provided a reservoir 402 that stores an etch-assisting gasmaterial. An etch-assisting gas material used in the embodimentcomprises perfluorododecane (F(CF₂)₁₂F) which is solid in a standardstate. A heater 403 heats an etch-assisting gas material together withthe reservoir to a requested temperature. The etch-assisting gasmaterial heated and vaporized is fed to a specimen surface from a nozzle404. Here, flow of a gas will be described with reference to FIG. 5which is an enlarged view. The etch-assisting gas material(perfluorododecane) 401 heated by the heater 403 vaporizes to flowtoward the nozzle 404 through a supplying hole 501. A valve 502 controlsON/OFF of supplying of the gas flowing into the nozzle 404, and ON/OFFof air pressure from an air tube 503 causes extension and contraction ofa bellows 504 to enable control. Gas flow rate can be controlled byheating temperature by the heater, and perfluorododecane is heated toabout 35° C. in the embodiment. A thermo sensor 405 monitors temperatureof the reservoir 402 to effect feedback of the same to the heater 403,thus realizing stable heating. Here, a thermocouple is used as thethermo sensor 405. An air is introduced into the air tube 503 through aconnector 406 shown in FIG. 4, and communication of electric signals ofthe heater 403 and the thermo sensor 405 is performed through afeedthrough 407. Connection to the vacuum chamber 112 which is aspecimen chamber is effected through a connection flange 408.

Here, while an explanation has been given to the case where anetch-assisting gas is solid, an etch-assisting gas material which isliquid can be likewise stored in the reservoir and heated by the heaterto be vaporized and supplied. In the case where an etch-assisting gasmaterial is liquid, however, sealing is needed to prevent the materialfrom leaking into a gas supplying line as it is liquid, and so anetch-assisting gas material which is solid is easy in handling than theliquid. In either case, as compared with an etch-assisting gas materialwhich is essentially gaseous, handling of an etch-assisting gas materialwhich is solid or liquid is easy by virtue of easiness in storage andeasiness in gas pressure regulation with temperature control.

FIG. 6 shows the positional relationship between connection of theetch-assisting gas supplying source 109 to the vacuum chamber 112 whichis a specimen chamber and a specimen. The etch-assisting gas supplyingsource 109 is fixed to a vacuum chamber wall 605 by the connectionflange 408 as described above. A line 601 indicates an optical axis ofthe ion-bean irradiating optical system 105 and an intersecting point ofthe optical axis and the semiconductor wafer 101 defines a processedpoint, so that the nozzle 404 is caused to approach the intersectingpoint. While an adjustment mechanism for a position of the nozzle isomitted in the drawing, adjustment mechanisms in three directions areactually provided and it is possible to adjust a position of the nozzleclose to a processed point. Actually, efficient gas supplying is enabledby causing a tip end of the nozzle 404 to approach a distance of severalhundreds microns to a processed point. The etch-assisting gas supplyingsource 109 comprises a valve controller 602 that controls an airpressure for opening and closing of the valve, a heater controller 604,and a thermo sensor controller 603, and these controllers are controlledby the controller 110 for the etch-assisting gas supplying source. Whilenot shown, in the case where a motor is provided to control a positionof the nozzle, a nozzle position controller is also controlled by thecontroller 110 for the etch-assisting gas supplying source.

The etch-assisting gas supplying source described above with referenceto FIGS. 4 to 6 is needed to be removed from the connection flange 408when an etch-assisting gas material is to be replenished. In case ofusing several kinds of etch-assisting gases to effect decoration ofprofile, it is troublesome to remove etch-assisting gas supplyingsources one by one from the flange, so that the apparatus is decreasedin operability. Further, in order to remove the etch-assisting gassupplying source from the flange, it is necessary to once open thevacuum chamber to the atmosphere, which is an obstacle to an improvementin throughput of specimen fabrication.

Hereupon, an etch-assisting gas material can be readily replenished bymaking a system, which supplies a gas to the etch-assisting gassupplying source, a cartridge type. Details for this will be describedbelow with reference to FIG. 7. An etch-assisting gas material 802 isstored in a cartridge 701 which is a portable type filling vessel, andthe cartridge is inserted into a cartridge holder 804 to be connected tothe etch-assisting gas supplying source. The cartridge holder 804 in theembodiment is cylindrical-shape with a side wall and a bottom cover 807coupled together by a hinge. A heater 703 and a thermo sensor 704 areembedded in the cylindrical-shaped side wall and respectively connectedto the heater controller 604 and the thermo sensor controller 603through feeder lines. Therefore, connecting terminals are provided on asurface of the cartridge holder to connect the heater 703 and the thermosensor 704, respectively, to the feeder lines. In addition, when theheater 703 is formed on an inner wall surface of the cartridge holder804, efficiency at the time of heating the cartridge becomes higher thanthat with an embedded type. Further, a heater may be embedded in acartridge.

For the purpose of easy comprehension of the cartridge 701, FIG. 8 showsa state, in which the cartridge 701 and the cartridge holder 804 areseparated from each other. The cartridge 701 comprises a body portionthat stores an etch-assisting gas material 802, and a neck portion thatconnects the body portion and the cartridge holder 804 to each other. Anopening is provided on an upper surface of the neck portion, and theopening is hermetically closed by a seal member such as a film 803, etc.The upper surface of the neck portion around the opening defines a jointsurface to the cartridge holder 804 or the etch-assisting gas supplyingsource. Provided inside the cartridge holder 804 is a recess, into whichthe neck portion of the cartridge 701 is inserted, and the recess isprovided with a projection 805. An O-ring 806 for vacuum sealing isprovided at a root of the projection 805, that is, a bottom surface ofthe recess. When the cartridge 701 is inserted into the cartridge holder804, the film 803 is torn by the projection 805. Further, the uppersurface of the neck portion of the cartridge 701 and the bottom surfaceof the recess of the cartridge holder are vacuum-sealed by the O-ring806. Thereby, a tube 702 in the etch-assisting gas supplying source andthe cartridge 701 are coupled to each other. Finally, when the bottomcover 807 is closed, the cartridge 701 is fixed in the cartridge holder.The cartridge 701 is appropriately heated by the heater 703 and thethermo sensor 704 and gas is supplied to the tube 702. Air pressure iscontrolled by the valve 705 whereby ON/OFF of the gas is made. Further,a valve may be provided in the vicinity of the neck portion (toward thebody portion or the cartridge holder), at which the body portion of theetch-assisting gas supplying source and the cartridge holder areconnected to each other, to shield the etch-assisting gas, therebymaking exhaust differentially relative to the valve 705.

Since the cartridge 701 is heated, it is preferably formed from amaterial of good thermal conductivity. Further, in order to store theetch-assisting gas material 802 therein, an inner wall surface of thecartridge 701 is preferably coated with a material, which is hard toreact with the etch-assisting gas material.

A manner, in which the cartridge holder 804 and the cartridge areconnected to each other, is not limited to the present system but mayresort to fitting or screwing. In this case, while the cartridge can befixed to the holder even without the bottom cover 807, the bottom coveris preferably provided in terms of thermal efficiency. Further, whilethe embodiment has been given by way of an example, in which thecartridge is shaped to comprise the neck portion and the body portion,it does not matter if the cartridge is shaped otherwise. Further, theterm “etch-assisting gas supplying source” is used in the abovedescriptions for convenience, it goes without saying that the cartridgetype mechanism described above is applicable to systems for supplyingother gases than “etch-assisting gas”.

As described above, the etch-assisting gas supplying source is made acartridge type whereby it becomes not only easy to replenish a gas butalso possible to quickly and readily exchange the gas for a preferableetch-assisting gas. Accordingly, the apparatus is improved inoperability and fabrication of specimens is increased in throughput.

Since quick exchange of kinds of etch-assisting gases is made possible,a plurality of kinds of gases can be made to flow through one gassupplying system without an increase in stress of a user for theapparatus. Accordingly, it is possible to reduce the number of gassupplying systems required to be provided in a specimen fabricatingapparatus, thus enabling manufacture of an apparatus at low cost.

In addition, while one cartridge holder is provided for theetch-assisting gas supplying source in the embodiment, the provision ofa plurality of cartridge holders makes it possible to supply a pluralityof kinds of gases without exchange. Both in the case where one cartridgeholder is provided for the etch-assisting gas supplying source and inthe case where a plurality of cartridge holders are provided, there is apossibility that when a kind of gas is replaced by another, a gas havingbeen used remains as a contaminant in a gas path (tube). In order toeliminate the contaminant, cleaning is made by providing a device thatheats the gas path, separately providing gas supplying means for flowingof inert gases, etc. through the gas path, or mounting/supplying acartridge for inert gases.

With the use of the specimen fabricating apparatus, irregularities everymaterial can be formed on a section by performing a processing of a holewith FIB and FIB processing while supplying a gas to a requested sectionas formed. Details of processing sequences will be described insubsequent embodiments.

A most simplified model will be described with respect to reactions ofan etch-assisting gas with Si and SiO₂. First, a CF etch-assisting gasmaterial comprises CnFm. Here, n and m are positive integers. Here, m<4nis assumed. Further, reaction products comprise SiF₄, CO₂, O₂, and SiC,which assume stable configurations. Among these substances, threesubstances, that is, SiF₄, CO₂, and O₂ are volatile and are extinguishedby evacuation. On the other hand, SiC remains on a specimen surface.Further, it is assumed that Si and SiO₂ are the same in number ofadsorption sites of an etch-assisting gas. Under the above assumptions,a chemical reaction formula of SiO₂ is as follows.4nSiO₂+4CnFm→mSiF₄↑+4nCO₂↑+(4n−m)Si  (1)Also, a chemical reaction formula with Si is as follows.(m+4n)Si+4CnFm→mSiF₄↑+4nSiC  (2)

When the formula (1) and the formula (2) are standardized per reactionadsorption site in order to make a comparison between rates, at whichone Si and one SiO₂ are removed, the formula (1) is converted into aformula (3) and the formula (2) is converted into a formula (4)SiO₂+(1/n)CnFm→(m/4n)SiF₄↑+CO₂↑+((4n−m)/4n)Si  (3)Si+(4/(m+4n))CnFm→(m/(m+4n))SiF₄↑+(4n/(m+4n))SiC  (4)

That is, with SiO₂, what is removed from one SiO₂ is only a part ofSiF₄, so that a coefficient (m/4 n) in the formula (3) indicates a rateas removed. Likewise, with Si, what is removed from one Si is a part ofSiF₄, so that a coefficient (m/(m+4n)) in the formula (4) indicates arate as removed. Based on the results, a ratio of SiO₂ and Si, which areremoved by the reaction, is indicated by a formula (5) where N(SiO₂) andN(Si), respectively, indicate removable numbers of SiO₂ and Si peradsorption site.

$\begin{matrix}\begin{matrix}{{{N\left( {SiO}_{2} \right)}/{N({Si})}} = {\left( {{m/4}n} \right)/\left( {m/\left( {m + {4n}} \right)} \right)}} \\{= {{{\left( {m + {4n}} \right)/4}n} = {1 + {{m/4}n}}}}\end{matrix} & (5)\end{matrix}$

Therefore, it is indicated that a sputter ratio in this reaction issurely larger than 1, that is, SiO₂ is larger in sputter rate than Si.Further, it is found that m/n is preferably large in order to increasethe sputter ratio. Further, in the case where O is contained in a CFetch-assisting gas material, in contrast to an effect that Si remains asSiC as indicated by the formula (2) and the sputter is constrained,there is a possibility that O possibly decomposes SiC and there is afear that a sputter ratio of SiO₂ and Si decreases.

What is described above is a model assumed in most simplification andthe model does not always react actually in this way, but it can begrasped as a tendency and so can be made use of as a search guidelinefor an etch-assisting gas material. Further, for adsorption of anetch-assisting gas, it is advantageously solid or liquid in a standardstate to be able to adequately produce an effect of the chemicalreaction. That is, it is found that an etch-assisting gas material whichis solid or liquid in a standard state and does not contain O isadvantageous to the section decoration. TABLE 1 indicates examples of CFgases.

TABLE 1 CHEMICAL REACTION STANDARD PRESENCE OR F/C No. FORMULA STATEABSENCE OF O RATIO 1 F(CF₂)₁₂F solid ABSENT 2.17 2 (CF₂)₁₅F₃N liquidABSENT 2.20 3 I(CF₂)₈I solid ABSENT 2.00 4 CF₃CONH₂ solid PRESENT 1.50 5CF₃COOH liquid PRESENT 1.50 6 CF₃CF₂COOH liquid PRESENT 1.67 7CF₃COHCOOH solid PRESENT 1.00 8 F(CF₂)₇COOH solid PRESENT 1.88 9 CF₃COFGASEOUS PRESENT 2.00 10 CF₃COCF₃ GASEOUS PRESENT 2.00 11 CF₄ GASEOUSABSENT 4.00 12 C₄F₈ GASEOUS ABSENT 2.00 13 C₅F₈ GASEOUS ABSENT 1.60 14C₃F₆ GASEOUS ABSENT 2.00 15 CHF₃ GASEOUS ABSENT 3.00

Nos. 4 to 15 among the examples represent gases already known asetch-assisting gases. It is found that No. 1, F(CF₂)₁₂F, which is beingused in the embodiment satisfies the condition that it is solid in astandard state and does not contain O. Actually, favorable sectiondecoration was confirmed by making an experiment with the presentapparatus. Other than F(CF₂)₁₂F, No. 2, (CF₂)₁₅F₃N, which is a kind offluorinert and No. 3, I(CF₂)₈I, satisfy the condition that they aresolid or liquid in a standard state and do not contain O and it wasconfirmed that favorable section decoration is possible.

Further, a sputter ratio of 1.5 times or more is expected in anexceedingly ideal case from the formula (5) provided that m/n assumes 2or more. Also, in this case, since adsorption of an etch-assisting gasis of course important, the condition that it is solid or liquid in astandard state and m/n is 2 or more becomes one of an efficient searchguideline for an etch-assisting gas material. It is found that among thegases in TABLE 1, Nos. 1 to 3 conform to this condition and areeffective in section decoration likewise as described above.

As a result of confirmation by actual experiments, in case of F(CF₂)₁₂F,the sputter rate of SiO₂ at the time of FIB etch-assisting is about 2.5times that of Si, so that a difference in level can be readily formed byless FIB irradiation. Further, it has been confirmed by experiments thatthe sputter rate of No. 2, (CF₂)₁₅F₁₅N, in TABLE 1 which is a kind offluorinert is about 1.9 times that of Si and the sputter rate of No. 3,I(CF₂)₈I, is about 1.6 times. Since these substances need less ion beamirradiation, that is, less dose, it is possible to reduce damage to asection. Further, an effect of boundary discrimination with SEM isadequately produced when a difference in level between SiO₂ and Si isformed to be 1 nm. In case of F(CF₂)₁₂F, section decoration can be madewithout little processing of a requested section and a section structurecan be observed substantially as it is since there is only a need ofprocessing of SiO₂ by 1.6 nm and Si by 0.6 nm in a direction of sectiondepth. In this case, while sediment containing C is formed on Si, thereis a need of dose of an order of magnitude larger than that in theprocessing at this time in order that sediment is actually accumulatedto enable observation with SEM, so that such sediment has no influenceon SEM observation in the processing of section decoration in theembodiment with less dose.

Further, since F(CF₂)₁₂F, (CF₂)₁₅F₃N which is a kind of fluorinert,I(CF₂)₈I, etc. are solid or liquid in a standard state, they have lessinfluences on an environment as compared with gases, and since they canbe processed in a short time as described above, they have an advantagethat it is possible to decrease a material consumption.

The present embodiment has illustrated an etchant material, whichcontains fluorine and carbon in molecules thereof and does not containoxygen and which is solid or liquid in a standard state, or an etchantmaterial, in molecules of which a ratio of fluorine to carbon in numberis 2 or more and which is solid or liquid in a standard state. By using,for example, F(CF₂)₁₂F, or (CF₂)₁₅F₃N which is a kind of fluorinert, orI(CF₂)₈I, etc. as an etchant material, it becomes possible to ensure alarge difference in sputter rate to effectively fabricate a specimen,profile of which is decorated. Further, by making an etch-assisting gassupplying source an apparatus of a cartridge type construction capableof exchanging an etch-assisting material, it becomes possible to readilyreplenish an etch-assisting material, thus enabling efficientlyfabricating a specimen.

With the use of the present specimen fabricating apparatus, it becomespossible to fabricating a section specimen which high contrastobservation in a device section by SEM becomes possible.

Embodiment 2

A method of fabricating a specimen, according to the invention, will bedescribed. FIG. 9 illustrates flow of fabrication of a specimen. Aspecimen fabricating apparatus used here is the apparatus shown FIG. 1.

(a) At the outset, FIB 104 processing is used to put marks 902, 903indicative of a position, in which a requested section 901 isfabricated.

(b) Subsequently, a rectangle, one side of which is defined by a lineconnecting between the marks, is set as FIB irradiation region and ahole 904 is processed by means of FIB processing. A length of a setrectangle along a requested section is determined by a region of therequested section, and a length in a direction perpendicular thereto isdetermined by a prospective angle of FIB irradiation at the time ofsection decoration described later and by a prospective angle at thetime of SEM observation. At this time, since FIB actually has a finitebeam diameter and beam flare or the like is involved, a processing issometimes made over a region, for which irradiation is set. In thiscase, since there is a fear that the requested section disappears, it isrequested that in view of influences thereby, a region of FIBirradiation be set apart a little from the marking line so as not tooverlap the same at the time of hole processing. Further, a depth ofhole processing is actually determined by a depth of a sectionstructure, of which observation is requested.

(c) A side wall 905 on a side of a requested section of arectangular-shaped hole thus fabricated is processed and reduced bymeans of a thin FIB in parallel to the requested section to expose therequested section 901.

(d) Subsequently, a specimen stage is inclined to enable irradiation ofFIB at a certain angle on the requested section. In case of theembodiment, the specimen stage is inclined at 45 degrees so as to enableirradiation at an angle of 45 degrees to the section. Of course, theangle of inclination is not limited to 45 degrees.

(e) In this state, an etch-assisting gas material 906 is supplied to thesection. As described in the embodiment, the etch-assisting gas materialis supplied through the nozzle 404 by opening the valve in a state, inwhich the reservoir of the etch-assisting gas supplying source is heatedto gasify the material. It is requested that the nozzle 404 be as closeto a specimen as possible within a region free of obstruction toirradiation of FIB, because supplying is enabled at high density,consumption of the gas supplying source is small, and the specimenchamber can be maintained high in degree of vacuum.

(f) In a state, in which the etch-assisting gas is thus supplied, FIB104 is irradiated on the requested section 905. It suffices that dosemake it possible to fabricate a difference of around 1 nm in levelbetween SiO₂ and Si.

In the procedure described above, it is possible to fabricate aspecimen, in which a difference in level is formed every structure onthe requested section. Here, while a requested region has been describedas a section, whether a requested region is a flat surface in parallelto a specimen surface does not matter, and a difference in level can bealso formed by irradiating FIB on an exposed flat surface whilesupplying the etch-assisting gas thereto in the same manner as describedabove. When a section of the specimen thus fabricated is observed withSEM, it is possible to obtain an image of structure observation in highcontrast owing to the edge effect.

Embodiment 3

An explanation will be given to a specimen fabricating apparatus forfabricating a specimen, a section of which is to be observed, from anextracted micro-sample according to the invention.

FIG. 10 shows a specimen fabricating apparatus functioning to extract amicro-sample. The apparatus is substantially the same in fundamentalconstruction as the specimen fabricating apparatus in FIG. 1 but isdifferent therefrom in having a probe 1001 for extraction of amicro-sample. The probe comprises a minute tip end having a tip enddiameter in the order of submicron. In the embodiment, a tungsten probeis used. The probe 1001 can be positioned by a probe driver 1002 and aprobe controller 1003. Further, the apparatus comprises a deposition-gassupplying source 1004. The supplying source is substantially the same inconstruction as an etch-assisting gas supplying source 1005 but what isstored therein is a deposition-gas. In the embodiment, tungsten carbonyl(W(CO)₆) is used as the deposition-gas material but the material is notlimited thereto. Further, the apparatus comprises a sample-carrierholder 1006 that places thereon a sample-carrier for fixation of anextracted micro-sample.

FIG. 11 illustrates a method of fabricating a specimen with the use ofthe apparatus.

(a), (b) At the outset, FIB 1101 is used to process three rectangularholes 1102, 1103, 1104 along three sides around a requested section.

(c) Subsequently, a micro-sample 1107 supported on an original sampleonly by a residual area 1106 can be fabricated by inclining a specimenstage and processing a trench 1105.

(d) Subsequently, the specimen stage is returned to an original positionfrom the inclined position and the probe driver 1002 brings a tip end ofthe probe 1001 into contact with the micro-sample 1107. Subsequently,FIB 1101 is irradiated on a region including the tip end of the probewhile a deposition-gas 1108 is supplied from the deposition-gassupplying source 1004, whereby a deposition film 1109 (W film in theembodiment) can be formed and (e) the micro-sample 1107 and the probe1001 can be fixed together.

Thereafter, the micro-sample can be separated from the original sampleby removing the residual area 1106 by means of FIB processing (f), (g).

The micro-sample 1107 thus separated is brought into contact with asample-carrier 1110 by driving of the probe (h).

The micro-sample and the sample-carrier are fixed together by forming adeposition film 1111 on the contact in the same way as described above(i).

Thereafter, the tip end of the probe is subjected to FIB processing toachieve separation of the probe whereby the micro-sample 1107 can bemade independent.

Subsequently, fabrication of a section will be described with referenceto FIG. 12.

(a), (b) FIB 1101 is irradiated in parallel to a requested section toperform a processing so as to expose the requested section 1201.

(c) Finally, the sample-carrier holder is inclined to enable irradiationof FIB at a certain angle on the requested section.

In the embodiment, nothing obstructs in front of the requested sectionunlike the case where one surface of the hole is made the requestedsection as in Embodiment 1, so that it is possible to irradiate FIBperpendicularly to the requested section (d), (e).

A specimen, the requested section of which is decorated, can befabricated by irradiating FIB 1101 in this posture to performetch-assisting while supplying an etch-assisting gas 1202. The specimenthus fabricated can be observed in higher contrast than that in case ofEmbodiment 1. The reason for this is that since a section to be observedin Embodiment 1 is present in the hole, it is hard to take secondaryelectrons into the detector at the time of SEM observation and yield ispoor. In contrast, since nothing obstructs in front of the requestedsection fabricated in the present embodiment, it is possible toefficiently detect secondary electrons to make observation in highcontrast. Further, while an angle of SEM observation corresponds tooblique looking-into in Embodiment 1, observation from a vertical isenabled in the present embodiment. Thereby, since observation of anaspect ratio in actual size is enabled, it is possible to increase theresolving power especially in a longitudinal direction. Further, sinceprimary electrons of SEM invade an interior of a section to some extentdepending upon acceleration voltage, detection of secondary electronsmakes estimated information in a region of invasion. With asemiconductor device to be observed, estimation in a directionperpendicular to a section does not cause an important problem since thestructure is the same in a shallow region, but it is necessary to payattention to understanding of a structure from an observed image sinceinformation is estimated in an oblique direction in the case whereobservation is made in oblique entrance as in Embodiment 1. In contrast,the present embodiment, which affords vertical observation, has anadvantage that less care suffices.

By using the specimen fabricating apparatus according to the presentembodiment, it is possible to fabricate a specimen, which enables SEMobservation from a vertical and of which a section is decorated.

Embodiment 4

In the present embodiment, an explanation will be given to a FIB-SEMapparatus that affords SEM observation on the spot after a section isfabricated by FIB etch-assisting.

FIG. 13 shows a construction of a FIB-SEM apparatus. The presentapparatus is the same in fundamental construction as the specimenfabricating apparatus shown in FIGS. 1 and 10 but the present apparatusdiffers therefrom in that a scanning electron beam irradiating opticalsystem 1301 is installed in the same specimen chamber. The SEM isobliquely provided relative to a specimen stage. This is because asection fabricated is made easy to observe without inclining thespecimen stage and a section being subjected to FIB processing can bemonitored by SEM at the time of formation of a requested section.Thereby, SEM observation can be made without exposing a specimen, asection of which is decorated, to the atmosphere and an observed imageof a section with high reliability can be obtained without care forcontamination in the atmosphere. Further, since observation can be madeon the same spot without movement to a separate SEM apparatus, there isan advantage that time for analysis is shortened. Further, since asection being subjected to FIB processing can be monitored by SEM at thetime of formation of a requested section, it becomes also possible tofabricate a requested section in a further correct position.

Further, with the present apparatus, FIB irradiation for etch-assistingcan be made perpendicularly to a requested section and SEM observationcan be made even when a micro-sample is not transferred to a samplecarrier as in Embodiment 3. The reason for this is that since a probe1302 is provided to be able to extract a micro-sample in the same manneras in Embodiment 3 and a probe rotating mechanism is provided, it ispossible to incline a micro-sample fixedly left on the probe and toarrange a requested section perpendicularly to FIB and SEM.

This method will be described with reference to FIG. 14.

(a), (b) The procedure up to extraction of a micro-sample 1401 is thesame as that shown in FIG. 12.

(c) A requested section 1402 while being fixed by the probe 1302 isprocessed by means of FIB 1404.

(d) Thereafter, the probe 1302 is inclined.

(e) Subsequently, a specimen with a section thereof decorated can befabricated by irradiation of FIB 1404 while an etch-assisting gas 1403is supplied. In this state, it is possible to irradiate FIB 1404 and tomake SEM observation.

With the use of FIB-SEM according to the present embodiment, it ispossible to realize observation of a section in a short time and with afurther high reliability.

Embodiment 5

In the present embodiment, an explanation will be given to a FIB-SEMapparatus that affords SEM observation on the spot after a section isfabricated by FIB etch-assisting and comprises an inclined ion-beamirradiating optical system.

FIG. 15 shows a construction of the FIB-SEM apparatus comprising aninclined ion-beam irradiating optical system 1501. A large difference inconstruction between the apparatus and the FIB-SEM apparatus, accordingto Embodiment 4, shown in FIG. 13 is that a specimen stage 1502 is notinclined. Thereby, the mechanism for the specimen stage is made simpleand an area required for a specimen chamber 1503 can be substantiallydecreased in an apparatus conformed to a wafer having, for example, φ300mm, so that the construction is advantageous in terms of cost andpositional accuracy. In this case, however, when the FIB optical systemis mounted perpendicularly to a specimen surface as in FIG. 13, aprocessing of a hole for exposure of a requested section is possible butFIB irradiation for etch-assisting for decoration of a section cannot bemade at a certain angle to a requested section. Therefore, theconstruction comprises the ion-beam irradiating optical system 1501inclined relative to a specimen surface as shown in FIG. 15. While anangle of inclination is optional, an inclination of, for example, 30degrees is adopted in the present embodiment.

Fabrication of a specimen with the use of the apparatus and a method ofobserving a section will be described with reference to FIG. 16.

(a) First, a rectangular region, one side of which is defined by arequested section 1602, is set in order to expose the requested section,and irradiation of FIB 1601 is made. At this time, adjustment isaccomplished by rotating the specimen stage so as to make the requestedsection be in parallel to a direction, in which the FIB optical systemis inclined. Actually, as described with respect to Embodiment 2, aprocessed region is set apart a little from a position of the actualrequested section so as not to include the position of the requestedsection. FIB processing in a rectangular shape can fabricate a processedhole 1603 in the form of a parallelogram as shown in the drawing, and asurface of the parallelogram is in parallel to the requested section.Successively, the requested section is processed and reduced by means ofa thin FIB with the positional relationship as it is, and thus therequested section 1602 is exposed.

(b) Thereafter, setting is accomplished by rotating the specimen stageby 90 degrees to enable irradiation of FIB 1601 on the requested section1602. With the ion-beam optical system, which is inclined by 30 degrees,according to the present embodiment, FIB is irradiated at 60 degrees onthe requested section. Section decoration is enabled by irradiating FIB1601 in this state while supplying an etch-assisting gas 1604 to therequested section 1602 from a nozzle 1605 in the same manner as in theembodiment described above. Thereafter, the specimen stage is rotatedback by 90 degrees to afford SEM observation of the decorated requestedsection 1602.

The present apparatus can also be provided with a probe, extraction of amicro-sample becomes possible as in the Embodiments 3 and 4, and thesame effect as that in the latter is expected.

FIB-SEM in the present embodiment is used to enable decoration of asection by means of etch-assisting also in an apparatus without amechanism for inclining a specimen stage.

Embodiment 6

In the present embodiment, an explanation will be given to sectiondecoration by etch-assisting with the use of a projection type ion-beamapparatus (referred below to as PJIB).

FIG. 17 shows the PJIB apparatus. A projection mask 1702 capable ofprojecting a requested rectangular shape 1701 is selected andirradiation enables processing a rectangular hole. A difference to FIBis that no scanning is made owing to batch irradiation. Thereby, a largecurrent processing becomes possible and a short time processing isrealized. Of course, it is also possible to form a rectangular beamsmaller than a requested rectangle and to perform scanning with suchrectangular beam to form a target rectangular hole. Also in this case, aprocessing in a shorter time than that with FIB is enabled.

An ion beam is irradiated on a requested section thus formed while anetch-assisting gas is supplied thereto, but there is a problem. In caseof FIB, irradiation on the whole section is performed by basicallyexercising deflective control of a spot beam, and for a minute regioncorresponding to a FIB spot diameter, dead time corresponding to oneframe of deflective scanning passes away until FIB is subsequentlyirradiated after FIB is once irradiated. During the time, theetch-assisting gas can be adsorbed. In case of PJIB, however, when batchirradiation is performed on a requested section, an ion beam isconstantly irradiated on the requested section during the irradiation,so that it is not possible to gain time, during which an etch-assistinggas is adsorbed. In this case, a sufficient chemical reaction does nottake place and physical sputtering becomes a main sputtering, so that arequested difference in sputtering rate cannot be obtained everymaterial in a section structure and section decoration cannot be madeefficiently. Therefore, also in case of the PJIB apparatus,etch-assisting is made possible by simulatively forming FIB. That is,FIB can be formed by inserting a pinhole aperture 1703 midway a PJIBoptical system and forming a minute beam to perform scanning with adeflector. While a large current of PJIB is effective in hole processingin order to lessen a processing time, restriction of beam with thepinhole aperture does not cause a problem since a minute current issufficient for an irradiation beam for etch-assisting used in sectiondecoration. Thereby, section decoration can be realized by performingscanning and irradiation with a minute beam while supplying anetch-assisting gas in the same manner as in the embodiment describedabove. Also, decoration of a section can be accommodated by making anon-irradiation time with a blanker so that the gas is adsorbed.

Further, in the present embodiment, a processing with a large currentbecomes possible also in case of argon beam, which becomes small incurrent density when used as FIB, and therefore, manufacture innon-contamination like this can be realized, so that it becomes possibleto return a wafer after analysis to a semiconductor manufacturingprocess. Further, influences on a subsequent semiconductor manufacturingprocess can also be suppressed by filling the processed hole with, forexample, a deposition film, etc. to return the same to the processing.

With the PJIB apparatus according to the present embodiment, ahigh-speed hole processing is possible, so that it is possible to lessentime for analysis. Further, since a section for observation innon-contamination can be fabricated and influences on the semiconductormanufacturing process can be made small, in-line analysis becomespossible.

Embodiment 7

In the present embodiment, an explanation will be given to sectiondecoration with the use of an electron beam.

FIG. 18 shows an electron beam apparatus. While the apparatus is thesame in fundamental construction as SEM but difference is that anetch-assisting gas supplying source 1801 is mounted. Also with anelectron beam 1802, a processing is enabled by the use of anetch-assisting gas. While a processing for exposure of a requestedsection is not impossible with the etch-assisting gas and irradiation ofelectron beam, the electron beam is not practical since electron issmall in mass as compared with ion and an electron beam is extremelysmall in sputtering rate as compared with an ion beam. Therefore, incase of an independent electron beam apparatus as in the presentembodiment, it is preferable to introduce a specimen, a requestedsection of which is exposed by a separate processing apparatus. Theelectron beam 1802 is irradiated to the section while supplying theretoan etch-assisting gas such as perfluorododecane, etc. from a nozzle. Asdescribed above, while the processing speed is small as compared with anion beam, a difference in irregularities every material, which is assmall as 1 nm, is effective for a requested section, for which sectiondecoration is necessary, so that section decoration can be realized evenwith an electron beam. In particular, since an electron beam isnegligibly small in physical sputtering, the reaction is almost purelycomposed of chemical etchant to enable sputtering further relying on amaterial. Therefore, it is possible to realize decoration of a minutesection with lower damage. The section thus fabricated can be observedwith the SEM function of the present apparatus.

Further, since section decoration is possible even with an electronbeam, it is also possible in FIB-SEM illustrated in the Embodiments 4and 5 to make use of an electron beam of SEM for an etch-assistingsection processing after the processing of a hole. A processing fordecoration of a further minute section is made possible by the use ofthe electron beam etch-assisting apparatus according to the presentembodiment.

Since the invention produces an effect in examination and analysis of asemiconductor processing, it can be made use of for an improvement inyield in semiconductor manufacturing companies to contribute much toreduction in cost, or the like.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A specimen fabricating apparatus comprising: a specimen stage, onwhich a specimen is placed; a charged particle beam optical system toirradiate a charged particle beam on the specimen; an etchant materialsupplying source to supply an etchant material, which contains fluorineand carbon in molecules thereof, does not contain oxygen in moleculesthereof, and is solid or liquid in a standard state; and a vacuumchamber to house therein the specimen stage.
 2. The specimen fabricatingapparatus according to 1, wherein the etchant material is F(CF₂)₁₂F. 3.The specimen fabricating apparatus according to 1, wherein the etchantmaterial is (CF₂)₁₅F₃N.
 4. The specimen fabricating apparatus accordingto 1, wherein the etchant material is I(CF₂)₈I.
 5. The specimenfabricating apparatus according to 1, wherein the etchant materialsupplying source has a cartridge type construction which enablesexchange of the etchant material.
 6. The specimen fabricating apparatusaccording to 5, further comprising a cartridge holder to fix thecartridge, and wherein the cartridge holder comprises means to heat thecartridge.
 7. A specimen fabricating apparatus comprising: a movablespecimen stage, on which a specimen is placed; a charged particle beamoptical system to irradiate a charged particle beam on the specimen; anetchant material supplying source to supply an etchant material, inmolecules of which a ratio of fluorine to carbon in number is 2 or moreand which is solid or liquid in a standard state, to the specimen; and avacuum chamber to house therein the specimen stage.
 8. The specimenfabricating apparatus according to 7, wherein the etchant material isF(CF₂)₁₂F.
 9. The specimen fabricating apparatus according to 7, whereinthe etchant material is (CF₂)₁₅F₃N.
 10. The specimen fabricatingapparatus according to 7, wherein the etchant material is I(CF₂)₈I. 11.The specimen fabricating apparatus according to 7, wherein the etchantmaterial supplying source has a cartridge type construction whichenables exchange of the etchant material.
 12. The specimen fabricatingapparatus according to 11, further comprising a cartridge holder to fixthe cartridge, and wherein the cartridge holder comprises means to heatthe cartridge.
 13. A specimen fabricating method comprising the stepsof: processing a hole in the vicinity of a requested region of aspecimen by means of irradiation of a charged particle beam; exposingthe requested region by means of irradiation of the charged particlebeam; supplying an etchant material, which contains fluorine and carbonin molecules thereof, does not contain oxygen in molecules thereof, andis solid or liquid in a standard state, to the requested region asexposed; and irradiating the charged particle beam on the requestedregion as exposed.
 14. The specimen fabricating method according to 13,wherein the etchant material is composed of molecules, of which a ratioof fluorine to carbon in number is 2 or more, and is solid or liquid ina standard state.
 15. The specimen fabricating method according to 14,wherein the etchant material is F(CF₂)₁₂F.
 16. The specimen fabricatingmethod according to 14, wherein the etchant material is (CF₂)₁₅F₃N. 17.The specimen fabricating method according to 14, wherein the etchantmaterial is I(CF₂)₈I.
 18. The specimen fabricating method according to13, wherein the etchant material is F(CF₂)₁₂F.
 19. The specimenfabricating method according to 13, wherein the etchant material is(CF₂)₁₅F₃N.
 20. The specimen fabricating method according to 13, whereinthe etchant material is I(CF₂)₈I.
 21. A portable charging vessel usedfor a focused ion beam apparatus provided with an etch-assisting gassupplying source for supplying of an etch-assisting gas into a vacuumchamber, and storing therein the etch-assisting gas, wherein theportable charging vessel comprises an opening, through which a gas issupplied to a pipe, a joint surface vacuum-sealed to the etch-assistinggas supplying source, and a seal member to hermetically seal theopening, and wherein the etchant material contains fluorine and carbonin molecules thereof, does not contain oxygen in molecules thereof, andis solid or liquid in a standard state.
 22. The portable charging vesselaccording to 21, wherein the etchant material is F(CF₂)₁₂F, (CF₂)₁₅F₃N,or I(CF₂)₈I.